1. Field of the Invention
The present invention relates to a piston type compressor, and more particularly to a multicylinder compressor in which a plurality of cylinders are arranged around an axis.
2. Description of the Prior Art
In conventional multicylinder compressors used for, for example, air conditioners, a plurality of discharge valves, provided in correspondence with the respective outlet ports of a plurality of cylinders, are integrally formed as a single plate. Each valve guard for restricting the motion of each discharge valve and protecting the discharge valve is formed usually in the same shape as that of the discharge valve.
FIGS. 4A and 4B illustrate a part of a conventional multicylinder compressor. FIG. 4B depicts a vertical section of a valve guard. In FIG. 4B, valve plate 110 having outlet ports 113 is provided on an end of a cylinder block (not shown).
Inlet valve member 114 is provided on the cylinder block side of valve plate 110. Discharge valve member 111 is provided on the cylinder head side of valve plate 110. Discharge valve member 111 has discharge valves 111a for opening and closing the respective outlet ports 113. Each discharge valve 111a is restricted in opening motion by valve guard 116a. Valve guard member 116 has a plurality of valve guards 116a by the number corresponding to the number of discharge valves 111a (outlet ports 113). Valve guard member 116 is provided in discharge chamber 122 defined by the cylinder head, particularly by inside partition plate 123 of the cylinder head. Valve guard member 116 has center hole 126 for fixing the valve guard member to valve plate 110 via a bolt (not shown). Gasket 115 seals between valve plate 110 and inside partition plate 123.
As shown in FIG. 4A, inside partition plate 123 of the cylinder head is formed as a shape having a wave line. The interior of waved inside partition plate 123 is formed as discharge chamber 122. Each of valve guards 116a of valve guard member 116 radially extends from the center of the member toward each of inner side surfaces 123a of projecting portions 123b of waved inside partition plate 123. Discharge valve member 111 has substantially the same shape as that of valve guard member 116. Each valve guard 116a extends straightly from the central portion of valve guard member 116, and only the tip portion of the valve guard 116a is shaped along each inner side surface 123a of projecting portion 123b of waved inside partition plate 123 with a substantially constant distance. Therefore, the distance between each constriction portion 116b of valve guard member 116 and the inner side surface of waved inside partition plate 123 is greater than the distance between the tip portion of each valve guard 116a and each inner side surface 123a of projecting portion 123b.
As shown in FIG. 4B, valve guard 116a is curved such that the separation distance of the valve guard from valve plate 110 becomes larger as the valve guard extends outwardly.
In such a conventional multicylinder compressor, the shape of discharge valve member 111 is designed in consideration of the rigidity of delivery valves 111a so as to decrease fluid loss through the discharge valves 111a small. Valve guard 116a is curved in vertical section to restrict the motion of discharge valve 111a and to aim the relaxation of stress of the restricted discharge valve 111a. And valve guard member 116 is star-shaped as described above. Therefore, valve guard 116a is relatively flexible similar to the discharge valve 111a. To increase the rigidity of valve guard 116a, each valve guard 116a and valve guard member 116 must be thick. In such a manner, however, the total weight and the cost of the compressor increase.